Relatives of the slain man involved in last week’s San Mateo shooting that left a young mother dead say they are considering hiring a private investigator to look into the case because the police account doesn’t ring true.

Police said they found 22-year-old Raymond Gee dead of a single bullet wound to the head in a back room of a home on Hobart Avenue after exchanging gunfire with him Nov. 25.

Ballistics tests and full autopsy results have yet to come back, but police believe Gee beat 24-year-old Loan Kim Nguyen and likely fired the shots that killed her as she handed her 1- and 3-year-old children to officers through a side window of her home.

San Mateo County Coroner Robert Foucrault said Monday that Nguyen had some bruises on her arms and other “injuries that are not consistent with the gunshot wounds.” But those injuries weren’t serious enough to cause her death, he noted.

Foucrault said his office is investigating Gee’s death as a suicide but has not made a final determination.

Police originally described the case as a home-invasion robbery and said Nguyen’s husband called them at about 9:39 a.m. on Nov. 25 after receiving a text message from his wife saying she was being robbed at gunpoint. They later said Gee stalked Nguyen online and in her quiet San Mateo neighborhood for several weeks before the shooting.

“We have confirmed that this was not a random attack, but rather an incident of stalking,” San Mateo police Chief Susan Manheimer said at a news conference last Wednesday.

But Gee’s family questioned the stalking theory Sunday and said he was likely collecting a debt from Nguyen. Gee told friends that someone owed him money and he may have known Nguyen through his work at a party promotion company several years earlier, his relatives said.

“We don’t know how much it was, but it must have been pretty significant for him to pursue her in that manner,” Gee’s aunt, Maggie Tao, said through a translator.

The family also expressed disbelief that the friendly, mild-mannered young man they knew would attack a woman with children present and open fire on authorities.

“He was a happy, charming, funny guy,” said Gee’s older sister, Jackie Gee. “He would always be trying to make people comfortable. He was always the first to help, especially if his family got into situations or his close friends.”

Jackie Gee said her brother had taken a break from community college and was working at a medical clinic in San Francisco and as a valet parking attendant to help take care of their mother, who developed symptoms of schizoaffective and bipolar disorders several years earlier. She added that her brother had no history of mental illness or emotional instability.

“Out of all my friends, he was the one that really stood out,” said Andrew Ngin, who attended middle school and high school with Gee. “He was a really happy person. I’ve never seen him mad or angry.”

Gee grew up in San Francisco, where he attended Herbert Hoover Middle School and Abraham Lincoln High School, from which he graduated in 2004. He was heavily involved with his large extended family, often babysitting for a 3-year-old cousin or helping older cousins with their homework, relatives said.

In February, police stopped Gee for a traffic violation and discovered marijuana and a gun in the trunk of his car, relatives said. According to the San Francisco County Superior Court, Gee received a sentence this summer of three years probation and 10 days in county jail on drug and gun charges.

At the time of the shooting, he was living in a halfway house in San Francisco’s Sunset District, with a strict curfew as part of that sentence, relatives said.

“He was taking responsibility for it — he was doing whatever he needed to do,” Jackie Gee said.

Janice Dirden-Cook, project director for the University of San Francisco’s Upward Bound youth program, said Gee was “a very popular student” when he attended the program from 2002 to 2004.

“All of us here were just shocked and stunned that he would be involved in something like this,” Dirden-Cook said Monday. “It seems so a-typical of his personality when he was here.”

Relatives said Gee seemed normal in the days before the shooting, washing the family’s two dogs and driving his mother to a dermatology appointment in El Cerrito on Nov. 24. The morning of his death, Gee even vacuumed his room at the halfway house, they said.

San Mateo Deputy Police Chief Mike Callagy said Monday he couldn’t release any further details on the case, such as how police determined Gee stalked Nguyen or whether they had confirmed that a gun found at the scene belonged to the suspect. He added that new information, including results from ballistics tests on the bullets that killed Nguyen and Gee, would become available later in the week.

“We just want to see the truth come out, the absolute truth,” Jackie Gee said. “We express condolences for (Nguyen’s) family, but how they’ve (police) treated Raymond — it’s not him at all.”